Biotechnology. Chapter 20. Biology Eighth Edition Neil Campbell and Jane Reece. PowerPoint Lecture Presentations for

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1 Chapter 20 Biotechnology PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

2 Concept 20.3: Cloning organisms may lead to production of stem cells for research and other applications Organismal cloning produces one or more organisms genetically identical to the parent that donated the single cell

3 Cloning Plants: Single-Cell Cultures One experimental approach for testing genomic equivalence is to see whether a differentiated cell can generate a whole organism A totipotent cell is one that can generate a complete new organism

4 Fig EXPERIMENT RESULTS Transverse section of carrot root 2-mg fragments Fragments were cultured in nutrient medium; stirring caused single cells to shear off into the liquid. Single cells free in suspension began to divide. Embryonic plant developed from a cultured single cell. Plantlet was cultured on agar medium. Later it was planted in soil. A single somatic carrot cell developed into a mature carrot plant.

5 Cloning Animals: Nuclear Transplantation In nuclear transplantation, the nucleus of an unfertilized egg cell or zygote is replaced with the nucleus of a differentiated cell Experiments with frog embryos have shown that a transplanted nucleus can often support normal development of the egg However, the older the donor nucleus, the lower the percentage of normally developing tadpoles

6 Fig EXPERIMENT Frog embryo UV Frog egg cell Frog tadpole Less differentiated cell Fully differentiated (intestinal) cell Donor nucleus transplanted Enucleated egg cell Egg with donor nucleus activated to begin development Donor nucleus transplanted RESULTS Most develop into tadpoles Most stop developing before tadpole stage

7 Reproductive Cloning of Mammals In 1997, Scottish researchers announced the birth of Dolly, a lamb cloned from an adult sheep by nuclear transplantation from a differentiated mammary cell Dolly s premature death in 2003, as well as her arthritis, led to speculation that her cells were not as healthy as those of a normal sheep, possibly reflecting incomplete reprogramming of the original transplanted nucleus

8 Fig TECHNIQUE Mammary cell donor Egg cell donor 1 2 Cultured mammary cells 3 3 Egg cell from ovary Cells fused Nucleus removed RESULTS Grown in culture Implanted in uterus of a third sheep Embryonic development Nucleus from mammary cell Early embryo Surrogate mother Lamb ( Dolly ) genetically identical to mammary cell donor

9 Since 1997, cloning has been demonstrated in many mammals, including mice, cats, cows, horses, mules, pigs, and dogs CC (for Carbon Copy) was the first cat cloned; however, CC differed somewhat from her female parent

10 Fig

11 Problems Associated with Animal Cloning In most nuclear transplantation studies, only a small percentage of cloned embryos have developed normally to birth Many epigenetic changes, such as acetylation of histones or methylation of DNA, must be reversed in the nucleus from a donor animal in order for genes to be expressed or repressed appropriately for early stages of development

12 Stem Cells of Animals A stem cell is a relatively unspecialized cell that can reproduce itself indefinitely and differentiate into specialized cells of one or more types Stem cells isolated from early embryos at the blastocyst stage are called embryonic stem cells; these are able to differentiate into all cell types The adult body also has stem cells, which replace nonreproducing specialized cells

13 Fig Embryonic stem cells Early human embryo at blastocyst stage (mammalian equivalent of blastula) Adult stem cells From bone marrow in this example Cells generating all embryonic cell types Cells generating some cell types Cultured stem cells Different culture conditions Different types of differentiated cells Liver cells Nerve cells Blood cells

14 The aim of stem cell research is to supply cells for the repair of damaged or diseased organs